1. Field of the Invention
The present invention relates to a cooling structure that prevents a heat source included in a housing from becoming too hot and thereby prevents heat fatigue of various devices provided adjacently to the heat source, and an image forming apparatus equipped with the cooling structure.
2. Description of the Related Art
An image forming apparatus equipped with a cooling structure as is described in Japanese Unexamined Patent Publication No. 2004-138844 is known in the related art. This image forming apparatus is configured in such a manner that a toner image is obtained by forming an electrostatic latent image on the peripheral surface of the photosensitive drum according to image information and supplying toner to the electrostatic latent image, and after the toner image is transferred onto a sheet of paper, the toner image on the sheet of paper is subjected to fixing processing by heating, after which the sheet of paper is discharged to the outside of the apparatus.
In the image forming apparatus of this kind, a fixing device that applies the fixing processing to the toner image on the sheet of paper by heating becomes a heat source, and the internal temperature of the apparatus main body is increased. A photosensitive unit provided with the photosensitive drum comprising a precision instrument is provided adjacently to the fixing device on the upstream side in the paper transportation direction, and heat transferred from the fixing device to a transfer portion raises a problem that the photosensitive drum is affected adversely by heat distortion or the like.
Such being the case, the image forming apparatus described in Japanese Unexamined Patent Publication No. 2004-138844 cited above adopts a cooling structure formed by providing plural fins in a protruding form to the frame made of synthetic resin and forming the housing of the fixing device, and by covering the fins with a metal foil.
According to this cooling structure, heat generated inside the fixing device is removed efficiently by an air flow that circulates throughout the apparatus via the metal foil covering the fins and having satisfactory heat conductivity. It is thus possible to effectively prevent an event that fixing device becomes so hot that various devices inside the apparatus are adversely affected.
Incidentally, besides the fixing device, a power supply unit that distributes power to various devices installed inside the apparatus main body and driving motors that drive various devices installed inside the apparatus main body are present within the image forming apparatus, and heat released from these heat sources are by no means negligible. The cooling structure described in JP-A-2004-138844 cited above, however, is applicable to the fixing device alone, and has a drawback that the versatility is poor.
This drawback may be overcome by providing fins to the power supply unit and the driving motors and covering these fins with a metal foil. This configuration, however, increases volumes of the power supply unit and the driving motors, which in turn raises a new problem that a limit is imposed in reducing the image forming apparatus in size.